I would take Faber over Belfort... he won 4 fights to Vitor's 3 they both had 3 finishes in their fights and all of Faber's win's were top 10's in his division and his opponents were tanked higher overall then Vitor's
I'd take Pettis over Faber or Vitor. Only fought twice, but was dominant and took out a solid champion in Henderson. Even when Faber was winning I still never got the feeling it was leading to a title. As far as gate keepers go, he's on top with a solid gold gate. As for Vitor, he beat a well past prime Hendo, vastly overrated Bisping and Rockhold who'll be fringe top 10 while in the UFC.